Properties of SnO2 based gas-sensing thin films prepared by ink-jet printing

SnO2 precursor inks with appropriate viscosity and surface tension were prepared using the sol–gel technique with anhydrous ethanol as the primary solvent. The inks were printed on both alumina ceramic and silicon substrates using an ink printing apparatus produced by modifying a commercial printer. SnO2 based gas-sensing films with different thicknesses and additives were formed, and the morphologies and electrical properties of these films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and an instrument designed to measure the gas sensing abilities of the films. A linear relationship was observed between the natural logarithm of the electrical resistance of the SnO2 films and the reciprocal of the films’ absolute working temperature in the range between 20 °C and 265 °C. The electrical and gas-sensing properties of the films changed significantly with the thickness of the films. The film thickness can be easily adjusted by modifying the number of printing events. The SnO2 films selectivity for various gases could be modified by utilizing different additives. This work also showed that ink-jet printing was a convenient and low-cost method to prepare gas-sensing films with controlled film thickness and additive level.